Due to deforestation less and less c02 is being taken out of the atmosphere

#4 Engaged Climate Change

“we don't need to overreact to global warming and sacrifice cheap and efficient energy (fossil fuels and other oils) just to try to reduce global warming”

Absolutely. Energy and the costs of its extraction definitely plays a huge role in the way we view global warming. However, there are a few misconceptions implied or explicitly mentioned in your comment:

1. Fossil fuels and other oils are very inefficient energy sources. A large amount of energy is wasted when extracting the energy present in these fuels. However, you are right in the sense that they are cheap. It is definitely cheaper, in a fiscal sense, to extract energy from fossil fuels as we utilize the same processes we used in the 1970s. But, we do pay a price - the price of the reluctancy to explore new ways of developing energy and the price of losing certain species due to global warming, and at some point, the areas we have once cherished in our lives.
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2. Environmentalists should not be against fossil fuels themselves, they are against the method of their extraction. Finding a method that emits less carbon dioxide in the atmosphere, and a method that extracts more energy from these fossil fuels is expensive, both in terms of time and money. The research of such methods need funding which is currently negligible. If we begin investing our time and money into the development of such methods, not only will we emit less carbon dioxide into the atmosphere, but we get more energy per volume of fossil fuels we utilize to power our electrical grid.
3. New technologies are always expensive: but they pay off due to their efficiency (the ability to get more out of a fixed amount), due to the amount of positions it opens for research, and it pays off in knowledge - the more knowledgeable our society becomes, the more powerful it is in reaching a set goal faster, not just in the energy sector, but really in everything society might need to face.